If you feel tired or lethargic during workouts, you might be low on zinc. Zinc has always been known as an important mineral for immune system functioning and many other general body functions, but research suggests it may also play a major role in how much energy and stamina we have, and how sore we get, when working out. Usual dietary sources of zinc are oysters, red meat, and poultry, but if you're looking for other options fortified versions of cereal, granola, legumes, nuts, and wheat germ are also good choices.